WASHINGTON – Sen. Marco Rubio of Florida increasingly looks and sounds like a candidate for the White House.

On Friday, the conservative Republican courted party members in New Hampshire, which holds the first-in-the-nation presidential primary.

On ABC’s “This Week” on Sunday, Rubio said “I do” when asked if he’s ready to be commander in chief.

On Tuesday, he was at the National Press Club laying out a plan for restructuring Social Security and Medicare, the latest in a series of major policy speeches he’s delivered in the past year.

Rubio, who turns 43 later this month, has been mulling a run in what’s expected to be a wide-open GOP presidential primary in 2016. But he’s been careful to say he hasn’t decided and reportedly has been weighing a number of factors, including whether former Florida Gov. Jeb Bush will run.

But Rubio told the National Press Club audience he’s not waiting to see whether Bush, his political mentor and a party establishment favorite, declares his candidacy.

“When someone contemplates running for president of the United States, you do so based on a criteria you’ve established for yourself,” he said. “I don’t think those are decisions that you make with someone else’s decision in mind. And I would bet you if he was here today, he’d give you the exact same answer.”

Presidential expert Terry Madonna said it’s pretty clear Rubio is in the race even if he hasn’t announced.

“He’s running,” said Madonna, who directs the Center for Politics and Public Affairs at Franklin &amp; Marshall College in Lancaster, Pa. “He’s spending an awful lot of time saying he’s ready to run (and) preparing to run to not run.”

At public events covered by national media, Rubio is laying out a platform just as a candidate would. Many of his positions, such as reducing government regulation and taxes to promote economic growth, play well in the conservative circles needed to win the nomination.

Rubio also recently voiced skepticism that global warming is due mainly to human activity, a position that runs counter to the conclusions of the vast majority of scientists. Rubio’s view is shared by the GOP’s tea party wing, which excoriated him for co-sponsoring a comprehensive immigration bill last year that would provide undocumented immigrants a path to citizenship.

On Tuesday, the freshman senator detailed his ideas for preserving Social Security and Medicare, echoing themes championed by House Budget Committee Chairman Paul Ryan, the Wisconsin Republican who was Mitt Romney’s running mate in 2012.

Those ideas include raising the age at which people 55 and under can start collecting Social Security, reducing the growth of benefits for upper-income recipients, and eliminating the 12.4 percent payroll tax for those who have reached retirement age.

He’s also calling for creation of a Medicare premium support system, which would give seniors “a generous but fixed amount of money” to buy insurance from either Medicare or a private provider.

“If nothing changes, by the time I reach full retirement age at 67, Social Security and Medicare will have been insolvent for years,” Rubio said. “This is not a scare tactic, It is not a doomsday scenario concocted to spur action. It is a mathematical certainty if things remain unchanged. And the longer we wait to address this, the harder it will be to fix.”

National Democrats are certainly treating Rubio like a candidate. They’ve labeled him a climate change denier and wasted little time slamming his proposals.

“In 2012, the Romney-Ryan ticket ran on that plan and it was soundly rejected by t e voters,” said Michael Czin, spokesman for the National Democratic Committee. “Sen. Rubio’s plan is just the latest example of the Republican Party’s out-of-touch policies that benefit a few instead of extending opportunity for all.”

As for Rubio’s declaration that he’s prepared to be president, Madonna, the political scientist, said that’s a qualification only a campaign can validate.

“Obviously, the voters will ultimately decide who’s ready,” he said. “The issue comes down to convincing the voters.”